I am trying to receive some weak am radio stations on my KX3. I can tune them in on the kx3 just fine, however as soon as I plug in either the kx3 usb pc control cable, or the i/q 1/8" stereo cable, I get a loud hum on the kx3 up to s9 that knocks the signal out, additionally on the panadaptor, all the weak signals disappear. I can tune in the strong stations, but the weak stations are all gone.

I have heard of people using a ground loop isolators. Is this what I should be using in this case? Should I get one for each of the connections, one for the usb --> 1/8" cat cable as well as the i/q audio cable? Has anyone experienced similar issues? Also is the noise on the vfo frequency normal? If it is does the flex radio suffer from the same, or the other rigs with and if out that goes into an lp-pan?

I suppose it might help to say a little more here if you are still struggling. I basically use an External USB Sound Card with my KX3 to get rid of all the hum. You want to make sure you have a ferrite on the USB Cable as well.

The Isolator helps as well if you plan to use the I/Q signals. So the path looks like this:

Some PC's may cause more Hum than other. The equipment proximity advice given is also very relevant in some cases. In others you may have a devil of a time stopping hum. You also may want to check that your sound card settings in Control Panel are not creating a feedback loop that the KX3 aggravates when connected to the PC sound card. Check your input and output levels.

Google "SDR-1000 isolation" and you'll see that most of these issues have been figured out by others several years ago. No sense reinventing the wheel just because it's a different radio.

Most people figured out how to deal with RFI and PC's way back when the PC became a logging tool. Still doesn't stop some people from complaining about it and trying to make an issue of it. A properly designed and laid out ground system will nullify RFI issues regardless of whether a PC is involved with the radio or not and also regardless of the power level in use.73,Michael, W4HIJ

A DJ friend of mine had same problem using a USB disc jockey hardware device.Get a three prong adapter on the laptop charger. You are eliminating the safety ground from the computer. No issues or problems. No safety hazard. No hum!Run your laptop on battery problem go away; then it is definitely the charger.Fred

A isolated USB interface should be standard on all ham equipment. As usual ham equipment manufacturers are behind on the latest technology and trends.These isolated interfaces are just about standard on test equipment.

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